1. Field of the Invention
The present invention pertains to a dry cement storage and mixing system for handling dry cement having solid additives mixed therein and of a type particularly useful in cementing well casings and the like.
2. Background
In well cementing operations, dry cement having certain solid additives mixed therein is typically stored in one or more bulk storage tanks in the vicinity of the well drilling operation for use in forming a cement slurry which is pumped into the wellbore between the steel casing and the open hole to anchor the casing in place and improve the structural integrity of the formation through which the well has been drilled. Certain problems arise in blending and mixing dry cement compositions prior to the addition of water to the mix. For example, certain solid particle type additives which are blended with the cement itself have a tendency to separate from the cement material due to elutriation because of differences in particle size and due to settling of particles which are of different densities. This settling or segregation of the particles of cement and other additives usually requires additional equipment for reblending of the cement mixture and often results in a poor cement mix lacking the properties required of the material.
The problems associated with providing a properly blended or mixed dry cement material for oil well operations are aggravated by the relatively small capacities of storage vessels which typically must be portable and in certain instances must be designed to be accommodated on offshore drilling vessels or platforms. Moreover, the utilization of pneumatic conveying methods for transporting and mixing dry cement materials also, with conventional storage and handling equipment, tends to promote segregation of the cement by particle size and separation or poor mixing of the cement with the requisite additives used with the cement materials.
The abovementioned problems have been somewhat vexatious to artworkers in the development of cement mixing and storage equipment prior to the development of the present invention.